The Current Status of the ``Extended Solar Cycle'' as Observed in Fe XIV

Details The Current Status of the ``Extended Solar Cycle'' as Observed in Fe XIV The Current Status of the ``Extended Solar Cycle'' as Observed in Fe XIV

May 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...180.1104a&link_type=abstract

American Astronomical Society, 180th AAS Meeting, #11.04; Bulletin of the American Astronomical Society, Vol. 24, p.746

Astronomy and Astrophysics

Astronomy

2

Scientific paper

Investigation of the behavior of coronal intensity above the limb in Fe XIV emission (5303 Angstroms) obtained at the National Solar Observatory at Sacramento Peak over the last nineteen years has resulted in the confirmation of a second zone of solar activity at high latitudes separate from the Main Activity Zones (MAZ). Localized high-latitude intensity maxima are observed at 0.15 Rsun above the limb throughout the solar cycle. They persist long enough at a given latitude to be visible in long-term (e.g., annual) averages and thus form High-latitude Activity Zones (HAZ). We identify two types of HAZ. Poleward-moving PHAZ, which we identify with the ``Rush to the Poles'' phenomenon seen in polar-crown prominences, appeared near latitude 60(deg) in 1978 (possibly earlier at lower latitudes). In 1979 equatorward-moving EHAZ branched off from the PHAZ (which continued on to reach the poles in 1980) near 70 to 80(deg) . They evolved approximately parallel to the MAZ. Near solar minimum, the EHAZ evolved into the MAZ of Cycle 22, and the emission continues its monotonous path towards the equator, where it should disappear around 1998. As of early 1992, it is clear that the pattern seen earlier is repeating. The PHAZ became apparent near the beginning of 1988 near 60(deg) in the North and South hemispheres. The northern PHAZ reached the pole during late 1989 to 1990, and polar emission effectively ceased at the end of 1990. The southern PHAZ moved more slowly, and the southern-most emission regions reached the pole in mid-1991. South-polar emission was still occurring as of the latest observations. The EHAZ that are the precursors of sunspot Cycle 23 became clearly established in the Northern hemisphere near the beginning of 1990 at approximately 70(deg) . Currently the zone is at about 55(deg) . The appearance of the EHAZ in the South was less dramatic but probably began in mid-1990 near 70(deg) . Its current position is also near 55(deg) . These recent observations increase the evidence for parallel overlapping solar cycles that begin every 11 years but last for approximately 19-20 years.

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